[Devel] [PATCH RHEL7 COMMIT] ploop: Add comment about ploop_pvd_header::m_FirstBlockOffset

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-957.27.2.vz7.107.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-957.27.2.vz7.107.4
------>
commit 88dcb49e42b73e592e6980f815d97cfe906b6c47
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Tue Aug 20 13:32:42 2019 +0300

    ploop: Add comment about ploop_pvd_header::m_FirstBlockOffset
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 drivers/block/ploop/fmt_ploop1.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/block/ploop/fmt_ploop1.c b/drivers/block/ploop/fmt_ploop1.c
index 5ca9f257be31..f54b4bf2039c 100644
--- a/drivers/block/ploop/fmt_ploop1.c
+++ b/drivers/block/ploop/fmt_ploop1.c
@@ -659,6 +659,11 @@ static int expand_holes_bitmap(struct ploop_delta *delta,
 	if (!delta->holes_bitmap)
 		return 0;
 
+	/*
+	 * According to BUG_ON() in ploop1_prepare_grow(),
+	 * we do not support zero m_FirstBlockOffset
+	 * at least since 2013.
+	 */
 	md_off = vh->m_FirstBlockOffset >> log;
 	nr = md_off + vh->m_Size;